Gearcase Break In Procedures

LOWER UNIT AND STERNDRIVE BREAK-IN PROCEDURES

Gearcase assemblies are shipped without oil. Proper break-in and maintenance are critical to ensure longevity and performance. Follow these guidelines:
General Gearcase Break-In
  • Fill the unit with the manufacturer’s required gear oil to the recommended level.
  • Adjust RPM at idle to manufacturer’s specifications.
  • Ensure proper shift adjustment is maintained.
  • Jumping Out of Gear: If the unit will not stay in gear, the clutch dog may be rounded off. Rounded clutch dogs are caused by, but not limited to:
    • Improper shift cable adjustment
    • Inadequate shift travel
    • Idle RPM too high
    • Shifting too slowly
    • Note: Rounded clutch dogs are NOT covered by warranty.
  • Avoid full-throttle starts.
  • Do not operate at a constant speed for extended periods.
  • Shift into forward gear a minimum of 10 times during break-in, with moderate engine speed after each shift.
  • Do not exceed 75% of full throttle during the first 5 hours of operation.
  • During the next 5 hours, avoid maintaining full throttle for long periods.
OMC and Mercruiser Sterndrive Service Notice
  • When purchasing either an upper or lower assembly separately, the opposite piece must be disassembled and cleaned by the service center to validate the warranty. This is due to potential cross-contamination of the oil.
Overall Engine Break-In Procedures The first 10 hours of your new engine’s life are critical. Please use the following information as a guideline:
  • Do not perform break-in on a water hose.
  • Double your oil with a major manufacturer TCW-3 oil. (Excludes direct-injected engines.)
  • Use mid-grade octane fuel from a major manufacturer, without alcohol.
  • Liquid-cooled engines should be slowly brought up to normal operating temperature to avoid cold seizure.
  • For the first hour, operate the engine at a varied speed of 700-1500 RPM to break in new pistons and rings.
  • During the next 6 hours, operate the engine in gear at no more than 3000 RPM:
    • Accelerate using only enough throttle to bring the boat up on plane quickly, then reduce throttle to maintain minimum plane speed.
    • Vary engine speed by accelerating to 3/4 throttle for 1-2 minutes, then return to minimum plane speed.
  • During the final 3 hours, you may operate at wide-open throttle for periods of less than 2 minutes.
  • Important: Avoid operating at a constant speed of 3000-4000 RPM or continuous full throttle for the first 10 hours. This is the economy range where timing is at full advance and the carburetor or fuel injection runs lean, which could lead to overheating and piston detonation.
  • Re-torque cylinder heads after the 10-hour break-in period, once the engine has cooled.